This work describes the preparation and scintigraphic evaluation of the distribution patterns in dogs of a series of structurally related aminonitriles labeled with 20.4 min carbon-11. C-11 HCN was collected in water containing carrier NaCN following 22 MeV proton bombardment of 99 percent N2 - 1 percent H2 gas mixture. Ten C-11 gamma-N- alkylaminophenylacetonitriles and nine C-11 gamma-N- arylaminoarylacetonitriles were prepared from C-11 NaCN and the corresponding Schiff base, Ar-CH double bond N-R(Ar). All compounds showed initial blood pool distribution with accumulation of C-11 activity in brain, heart, lung, liver and kidney. Prolonged retention of activity in the blood pool was observed with gamma-N-methyl-, ethyl-, propyl- , isopropyl-, butyl-, isobutyl-, sec-butyl-, and tert- butylaminophenylacetonitrile. Several arylaminoarylacetonitriles showed pronounced accumulation of C-11 activity in brain, including gamma- anilino- and gamma-p-chloroanilinophenylacetonitrile, and, to a lesser extent, gamma-p-toluidino- and gamma-p- anisidinophenylacetonitrile, and gamma-anilino-p- tolylacetonitrile. The extent and rapidity of such accumulation suggests remarkably high extraction efficiency of these compounds by the brain. These arylaminonitriles, in addition to gamma-anilino-p-chlorophenyl- and gamma-anilino-p-anisylacetonitrile, showed marked accumulation of C-11 activity in lungs and liver with the major excretion of activity in bile. Gamma-p-anisidinophenylacetonitrile showed a significant retention of activity in heart. These results provide some correlation between chemical structure and distribution pattern of the compounds studied and suggest the diagnostic utility of some of these compounds for organ visualization and for measuring regional brain blood flow.